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Resources3D Printing DesignAll About Direct Metal Laser Sintering (DMLS) 3D Printing

All About Direct Metal Laser Sintering (DMLS) 3D Printing

Picture of Dean McClements
Written by
Aaron Lichtig
Updated by
 7 min read
Published September 23, 2020
Updated October 8, 2024

Learn more about this process for creating metal parts using a 3D printer.

DMLS part

Direct Metal Laser Sintering (DMLS) 3D printing is a metal-based manufacturing technology used to create complex metal parts. It uses a range of materials that include anything from copper to Inconel®. The aerospace, medical and turbomachinery industries are some notable users of the technology. DMLS was first introduced into the market in 1995 by a German company called EOS (Electro Optical Systems).

This article will describe how DMLS works, its advantages and disadvantages, as well as some of the key materials used.

What Is Direct Metal Laser Sintering 3D Printing?

A DMLS 3D printer is a powder-bed fusion technology. It is used to manufacture metal parts by directing a high-powered fiber laser beam at a single, thin layer of metal powder and fusing an outline of that layer onto the previous layers. The process is repeated for every successive layer until the entire metal part has been printed, one layer at a time, with each layer melted into the previous one. The term Direct Metal Laser Sintering (DMLS) was coined in 1995 when a German company called EOS (Electro Optical Systems) first commercialized it. EOS also owns the DMLS trademark.
The word "sintering" in DMLS is actually somewhat of a misnomer. Sintering involves heating a powdered material to the point where it coalesces into a solid mass without melting the material. According to EOS, DMLS is a German acronym that stands for “Direkt Metall Laser Schmelzen.” Schmelzen'' means "melt," not "sinter." Despite the English name of the process, Direct Metal Laser Sintering does not actually involve sintering the metal powder. Instead, it melts the metal particles together to form the part. This is why the process is also sometimes referred to as Direct Metal Laser Melting (DMLM).

Parts being made in a DMLS machine
Parts being made in a DMLS machine

Uses of Direct Metal Laser Sintering for Making Parts

Direct Metal Laser Sintering (DMLS) is used for the serial manufacture of complex industrial metal components that cannot be made economically—or at all—with other metal manufacturing technologies, such as CNC machining or metal injection molding. It's one of our most important 3D printing processes at Xometry. When parts are manufactured using traditional subtractive processes, they often need to be assembled from multiple components. However, DMLS 3D printing can create a monolithic part that eliminates the inherent weaknesses and complexities of assembled parts. DMLS printing is most often used in the aerospace, medical, turbomachinery, and automotive industries.

"It's a very difficult process. It's one of those processes where you're not only creating geometry, but you're creating the material. So I often equate that to if you imagine your Hewlett Packard printer that's on your desk, if you still have one of those, imagine that actually creating the paper as well. So, we're doing so many things inside of of a printing printing process that it makes it difficult for some people to comprehend. And with DMLS, it's on an off-the-charts scale."
Matthew Schmidt,
Senior Solutions Engineer

How DMLS 3D Printing Works

DMLS printers work by selectively melting a metal or metal alloy powder with a high-powered (up to 1000 W) fiber laser beam. The laser beam scans the cross-section of a part layer and melts the metal powder particles together. Some machines have up to four independent lasers that can all operate on the same layer simultaneously, effectively quadrupling the print speed.

Once a layer is complete, the print bed moves down, and another layer of metal powder is transferred to the print bed with a powder recoater. The DMLS system then fills the build chamber with an inert gas to prevent oxidation during printing. Once the complete part is printed, any support material must be removed.

The speed of a Direct Metal Laser Sintering printer is limited by how quickly the optical mirrors can be repositioned. This speed is often referred to as the “scanning speed," which indicates how quickly the laser can move across the powder bed to melt the metal particles. DMLS printers have a scanning speed of ~7 m/s. The largest DMLS machines have four lasers and can thus print in four locations simultaneously. This dramatically improves machine productivity and print speed. 

The accuracy of a laser-based powder-bed fusion printer depends primarily on the quality of the optical components and the accuracy of its laser. The typical fiber laser used on DMLS machines has a focal point from 40 to 100 microns in diameter, depending on the machine. This means that the smallest theoretical feature size is 40 microns. 

DMLS Schematic
DMLS Schematic

DMLS 3D Printing Materials

Common materials used in DMLS printing include:

  1. Aluminum Alloys (AlSi10Mg): This aluminum alloy is typically used for casting applications. It can be used on components with thin walls and fine features. This alloy also has good mechanical and thermal properties.
  2. Inconel® 718: Inconel® is a nickel superalloy often used in the aerospace industry, where it is useful for its ability to maintain high strength at extremely high temperatures. It is also highly corrosion resistant. 
  3. Titanium (Ti6Al4V): This titanium alloy has excellent mechanical and corrosion resistance properties. In addition, it is biocompatible, making it ideal for medical implants.
  4. Stainless Steel (316L): 316L is a very corrosion-resistant material. It is used extensively in industrial acid-producing facilities, specifically in handling sulphuric acid.
  5. Copper: Copper has excellent thermal and electrical conductivity. It is often used for heat exchangers and induction coils. Copper (Cu) and some copper alloys like CuCP and CuCrZr can be printed on DMLS printers.
  6. Case-Hardening Steel (20MnCr5): This material can be case hardened after printing. That makes it ideal for applications requiring superior wear resistance, such as gear wheels.
  7. Cobalt-Chrome (CoCr): This  CoCr alloy family has excellent corrosion resistance and maintains its mechanical properties at elevated temperatures. It is a nickel-free alternative to Inconel®. It is also biocompatible and used for components in gas turbines and orthopedic implants. 
Stainless steel part made by Xometry with DMLS 3D printing.
Stainless steel part made by Xometry with DMLS 3D printing.

Advantages and Disadvantages of Direct Metal Laser Sintering

Direct Metal Laser Sintering is one of the most mature and efficient metal printing technologies. Listed below are some of its key advantages:

  1. DMLS is capable of printing high-strength functional metal parts in a wide variety of metals.
  2. It is possible to print mixtures of plastic (nylon) and metal (aluminum).
  3. DMLS is a high-resolution printing process that can produce very small feature sizes. This is because the DMLS laser beam can be as narrow as 40 micrometers.

Disadvantages:

  1. DMLS parts need support during printing. This is due to the mass of the metal parts.
  2. DMLS parts can have internal stresses due to the high-temperature manufacturing process. Removing these internal stresses during printing requires multiple test samples and additional characterization. Alternatively, post-print heat treatment can also remove these stresses. However, both of these processes ultimately result in a higher cost per part.
  3. DMLS makes use of lower-powered lasers compared to SLM and EBM machines. Therefore, it produces a smaller melt pool and cannot print very high layers. This ultimately results in slower prints and, therefore, higher cost per part.

Differences Between DMLS and SLM 3D Printing

Both DMLS and SLM are powder-bed fusion printing technologies. SLM makes use of higher-power lasers, can handle bigger parts, and can incorporate up to 12 lasers. Thus, SLM is better suited to high-volume production, whereas DMLS is better suited to smaller volumes and more highly detailed parts. For more information, see our guide on DMLS vs. SLM 3D Printing

Xometry provides a wide range of manufacturing capabilities including CNC machining, 3D printing, injection molding, laser cutting, and sheet metal fabrication. Get your instant quote today.

  1. Inconel® is a registered trademark of Huntington Alloys division of Special Metals Corp., Huntington, WV.

Disclaimer

The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.

Picture of Dean McClements
Dean McClements
Dean McClements is a B.Eng Honors graduate in Mechanical Engineering with over two decades of experience in the manufacturing industry. His professional journey includes significant roles at leading companies such as Caterpillar, Autodesk, Collins Aerospace, and Hyster-Yale, where he developed a deep understanding of engineering processes and innovations.

Read more articles by Dean McClements

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